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From: Uwe Klein <u...@klein-habertwedt.de>
Newsgroups: comp.lang.tcl
Subject: Re: How to interrupt a task which is running in a thread?
Date: Fri, 28 Sep 2012 12:58:39 +0200
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Andy wrote:
> Another question, how to get output message? I mean the message generated by ping command.

#!/usr/bin/wish

button  .start  -text Start -command {handlecmd X start}
button  .stop   -text Stop  -command {handlecmd X stop}
grid    .start  .stop

# create a loop filedescriptor, there are various other ways
# to achieve the same:
set ::pfd [open |cat  RDWR  ]
fconfigure $::pfd -buffering none

# create an event handler for (returning) output
# and a proc to handle events:
proc outputevent {fd} {
         puts stderr PFD:[ gets  $fd ]
}
fileevent $::pfd readable [list outputevent $::pfd]

proc handlecmd {_id action} {
         upvar ::$_id id
         switch -- $action \
         start {
                 if {![catch {set id} cerr]} {
                         puts stderr "Task runs already"
                         return
                 }
		# redirect all output to a file desciptor:
                 set id [ exec ping localhost >&@ $::pfd & ]
         } stop {
                 if {[catch {set id} cerr]} {
                         puts stderr "Task does not run"
                         return
                 }
                 exec kill $id
                 unset id
         }
}

uwe